How to Hide MailOptin - Lite Admin Menus

function plt_hide_mailoptin_menus() {
	//Hide "MailOptin".
	remove_menu_page('mailoptin-settings');
	//Hide "MailOptin → Settings".
	remove_submenu_page('mailoptin-settings', 'mailoptin-settings');
	//Hide "MailOptin → Integrations".
	remove_submenu_page('mailoptin-settings', 'mailoptin-integrations');
	//Hide "MailOptin → Emails".
	remove_submenu_page('mailoptin-settings', 'mailoptin-emails');
	//Hide "MailOptin → Optin Campaigns".
	remove_submenu_page('mailoptin-settings', 'mailoptin-optin-campaigns');
	//Hide "MailOptin → User SyncNEW".
	remove_submenu_page('mailoptin-settings', 'mailoptin-fusewp');
	//Hide "MailOptin → Leads".
	remove_submenu_page('mailoptin-settings', 'mailoptin-lead-bank');
	//Hide "MailOptin → Statistics".
	remove_submenu_page('mailoptin-settings', 'mailoptin-statistics');
}

add_action('admin_menu', 'plt_hide_mailoptin_menus', 36);

Where do I put this code?